Mr. Jabba, the chief executive of a start-up medical device company, worked his way around two circular tables where more than three dozen preserved cadaver hearts — from neonatal to octagenarian — were available for holding, prodding and even poking with needles at a trade show for medical specialists.

The debate over the safety of cardiovascular stents has tended to dominate this year’s annual gathering of doctors who treat heart disease using technology rather than surgery. But Mr. Jabba represents the many people with interests besides stents who are attending the Transcather Cardiovascular Therapeutics show here at the Washington Convention Center, which runs through Thursday and has drawn about 12,000 participants.

Mr. Jabba mingled with a group of doctors at the convention’s Hands-on-Hearts exhibit, who were examining the ways various diseases and conditions had altered the anatomy of the hearts on display. His focus was whether any of the specimens contained a tiny defect that would allow blood to leak between the two upper chambers of the heart.

That congenital condition, which affects as many as 25 percent of adults, is the target of a device being developed by Mr. Jabba’s company, Ovalis, based in Mountain View, Calif.

The company, which Mr. Jabba said was a spin-off from Abbott Laboratories, is at work on a device that could close such holes, by way of a thin catheter tube threaded through the patient’s circulatory system. The standard treatment now is open-heart surgery.

Closing the holes without such surgery is seen as a potential multibillion-dollar business, because the defect has been linked to heightened risk of strokes and serious chronic migraine attacks.

Thomas Gunderson, who has followed the medical device industry for many years as an analyst for Piper Jaffray, the Minneapolis brokerage firm and investment bank, said that monitoring progress in the hole-closure field was his main reason for attending the convention.What is Mr. Jabba’s approach? “That’s still a secret,” he said with a smile, as he noted the presence of a senior executive from CoAptus Medical, a potential rival, who was chatting with doctors a few feet away.

CoAptus, based in Redmond, Wash., is working on technology to close the holes by heating them with radio energy using a catheter, instead of implanting a device.

There are skeptics at the convention as well, though.

At a scientific session Wednesday afternoon, Dr. Joseph P. Carrozza Jr., the chief of interventional cardiology at Beth Israel Deaconess Medical Center in Boston, urged his peers not to get carried away with hole-closure technology, which has already been used in thousands of younger patients who have had otherwise unexplained strokes, in the hope of preventing a recurrence.

Dr. Carrozza said that more than 98 percent of the 65 million Americans who have the defect will never experience the kind of stroke that closing the hole might prevent. “It’s not necessary, the complications are rare but devastating, and it’s expensive,” said Dr. Carrozza, who said the procedures cost hospitals more than $23,000 apiece.

The heart defect, known as patent foramen ovales, or P.F.O., can allow blood returned to the heart through the body’s veins to recirculate into the arteries — and reach the brain — without first passing through the lungs. It is a remnant of a stage in fetal development when an open passageway between the upper chambers of the heart allows the fetus to circulate oxygenated blood received from the mother.

Although the opening normally closes shortly after birth, it sometimes fails to do so completely. As many as one in four adults has the P.F.O. defect, with a small hole between the atria that is open all the time or that opens temporarily when the heart is under stress.

The condition generally goes unnoticed and untreated. But during the 1990’s, evidence began to accumulate that it might be linked to the 150,000 or so strokes that occur for no apparent reason in the United States each year — roughly 40 percent of all strokes.

More recently, the condition has also been linked to severe migraines that are accompanied by the visual hallucinations known as aura.

Suddenly, it appeared that the small companies developing P.F.O. closure devices as a possible protection against stroke might also have a lucrative opportunity to treat migraine.

As with coronary stenting, heart valve replacement and other heart procedures in so-called interventional cardiology, the goal of Ovalis and other companies looking at P.F.O. closure is to develop technology for treating the condition using thin catheters that can be inserted through a blood vessel in the groin and threaded up to the treatment site.

The company leading the P.F.O. pack at the moment is probably NMT Medical, which has completed a clinical trial in England. The trial results indicate that the company’s device reduced the frequency of severe migraines that resisted drug therapy, but it did not eliminate them.

NMT has been telling visitors to its booth at this year’s convention that federal regulators have agreed to let it test an improved version of its device in a larger trial in the United States, hoping for similar results. The company is scheduled to begin enrolling patients for that trial by the end of the year. Two other companies, AGA Medical and St. Jude Medical, have also begun migraine trials.

The giants of the device industry, including Johnson & Johnson, Medtronic and Boston Scientific, have also been exploring the field.

Such opportunities explain why entrepreneurs like Mr. Jabba; investors and analysts; and marketing teams from giant medical companies like Medtronic, Boston Scientific and Johnson & Johnson come close to outnumbering the doctors at the conference, according to the Cardiovascular Research Foundation, the nonprofit group that runs the event.